Recently, various types of information storage media have been developed and used to store digital data thereon. Examples of those storage media include rewritable optical disks, such as DVD-RAM disks and BD-RE (Blu-ray Disc Rewritable) disks, on which data can be rewritten an unlimited number of times and write-once optical disks, such as DVD-R disks and BD-R (Blu-ray Disc Recordable) disks, on which data can be written only once but which are inexpensive instead.
Some of those optical disk have a data storage layer and a label storage layer, which is located either deeper than the data storage layer when viewed from over the light incoming side of the disk or on the opposite side (i.e., the non-light incoming side) of the disk. Label information, which is information about characters and images representing the titles of contents such as recorded programs, is stored in the label storage layer.
According to the LightScribe technology, for example, a disk, including a label storage layer (or label storage side) on the other side thereof that is opposed to its light incoming side, is used. When an optical disk drive (such as that of a DVD recorder) that is compatible with the LightScribe technology is used, the titles of recorded programs, for example, may be stored on the label storage side. Then, it is easier for the user to know what content is stored on a given disk. For example, Patent Document No. 1 discloses a technique for writing (or printing) information on the label storage side with a laser beam.
To write label information by the LightScribe technology, however, the disk needs to be turned over once and then loaded again. Also, since the label information is writable on the label side only once, the label information stored on a rewritable disk such as a DVD-RAM does not always agree with the data that is actually and currently stored on the disk, thus possibly confusing the user unintentionally. Besides, it could take as long as about 30 minutes to write label information with a laser beam as is done in the LightScribe technology.
To overcome such problems, Patent Document No. 2 discloses various storage media with a sheet of electronic paper and techniques for displaying label information using a sheet of electronic paper. Data stored on a sheet of electronic paper can be updated in just one second or less, which is much shorter than the amount of time it takes to write label information with a laser beam. What is more, there is no need to turn over the storage medium in writing information on a sheet of electronic paper. Consequently, those problems to be caused by the LightScribe technology can be resolved.                Patent Document No. 1: Japanese Patent Application Laid-Open Publication No. 2005-44502        Patent Document No. 2: Japanese Patent Application Laid-Open Publication No. 2003-331560        